For a long time, cosmetic applicators in the form of brushes have been classically produced exclusively by inserting natural or synthetic fibers between two wires that were initially straight. Then these wires were twisted and secured the fibers that had been inserted between them in a particular configuration. Brushes of this kind are generally referred to as wire core brushes.
Wire core brushes have many advantages, but they have a critical disadvantage, namely that the spacing of the individual bristles of the bristle set from one another can only be varied within very narrow ranges. It is practically impossible to produce an applicator that has a bristle set that is truly uniform around and along the longitudinal direction. Instead, in wire core brushes, the bristle set is always the densest along a helix that follows the twisting of the wires, while being less dense in other regions.
Since it has become possible to produce ever more delicate injection molds, for approximately the last ten years, there has been an increase in the production of injection-molded brushes, even among those that are then used as mascara applicators. These are one-piece brushes in which the bristle support and the bristles protruding from it are produced from one and the same material, usually by means of injection molding.
In practice, there is in many cases a need to manufacture the bristle support on the one hand and the bristles that are fastened to it on the other out of different materials, which each take into account the individual requirements. It is thus useful, for example, to produce the bristle support out of a harder material in order to provide it with the necessary rigidity, while on the other hand, it is useful to produce the bristles out of a material that is softer than the material of the bristle support in order to thus provide them with the desired flexibility and above all, to prevent the bristles from giving a “prickly” feeling, haptically speaking.
In order to be able to fulfill this requirement, the Moltrusion® technique was developed, which is described by European patent EP 1 507 640 B1. The so-called Moltrusion technique is based on the concept of embodying the bristle support as a thin-walled tube, which is made of the material that should ideally be used for this purpose. This tube is inserted into the injection mold used to produce the bristles and is injection-filled from the inside out.
Because the plastic melt that subsequently forms the bristles is first injected into the inside of the bristle support tube and then forms the bristles due to the piercing of the outer wall of the bristle support tube, it is possible to produce bristles that have outstanding strength properties since this method provides the plastic molecules with a strength-enhancing orientation.
With the aid of the Moltrusion technique, however, it is only possible to produce one type of bristles. Up to this point, it has not been possible to produce different bristles on the same brush by respectively using the Moltrusion technique.
The object of the invention is to disclose a brush that has a bristle field composed of different injection-molded bristles, which can be efficiently produced and each have improved strength properties compared to conventionally injection-molded bristles.
Another object of the invention is to disclose a corresponding method.